Re: imapd and synchronous writes

Alan Cox (alan@cymru.net)
Tue, 19 Mar 1996 10:07:41 +0000 (GMT)

> > Modern EIDE drives with write-behind can also screw the
> > O/S's sync write ordering.
> The problem is not that of ordering, but of knowing when something has
> been committed to non-volatile storage. If, in fact, the drives
> inform the OS that they have committed a write before they in fact
> have, you've got some pretty unreliable drives.

They certainly seem to do exactly that.

> > Not true. {int fd = open(".", O_RDONLY, 0); int rc = fsync(fd); close(fd)}
> Since the namei() call could be a performance issue, systems which
> need this should provide a feature-test for applications to key off
> of. Some have suggested "__linux", but that's not a feature test.
> It's a system test.

BSD, System 5 and Linux all cache "." so the open of the file overhead is
so close to nil I doubt it matters.

Alan